This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-18892, filed Jan. 27, 2000 and No. 2000-174059, filed Jun. 9, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an airport facilities monitor system for monitoring airport facilities such as a number of lamps, sensor or the like to be installed on runways, taxiways or the like in the airport, the airport facilities monitor system using the power-line carrier technology.
In the prior art, the airport facilities monitor system for monitoring airport facilities constituted of a number of lamps, sensor or the like to be installed in the airport using the power-line carrier technology have a host station and, respectively through a rubber transformer, terminals (slave stations) connected in series to a power line derived from a fixed current generator CCR/CCT (called fixed current generator, hereinafter) for creating and generating a fixed current from a commercial alternative current source, lamps and sensors being connected respectively to these respective terminals.
There, both the host station and respective terminal perform the host-terminal communication, by transmitting in combination 1-bit information synchronized with the cycle of the power source waveform output from the fixed current generator. In short, the host station transfers the control signal sent from a central monitoring room side which is a higher order system to respective terminal through a power line by the combination of 1-bit information, and upon reception of this information, the respective terminal control the turning ON/OFF of the lamp based on the information contents. On the other hand, the respective terminal monitors the lamp and sensor status, transfers its monitoring information to the host station through the power line by the combination of 1-bit information, while the host station is constituted to transfer the monitoring information received from respective terminals to a monitoring control panel, which is a higher order system, through LAN, to display the status of lamps and the like of respective terminals on an operator console.
By the way, in such power-line carrier monitoring control system as mentioned above, in addition to a dedicated monitoring of burnt-out lamp, nothing but a predetermined number of lamps can be monitored and controlled, because little data amount can be treated by the power-line carrier and, besides, the transfer rate is low.
On the other hand, the fixed current generator in the aforementioned monitoring and control system, is the one designed to supply the power line with power of fixed current and, more concretely, as shown in FIG. 1, adopts a method to select a current waveform S2 of high amplitude between a low amplitude current waveform S1 and the high amplitude waveform S2 through the phase control at a convenient phase angle (60 degrees for example) from the zero cross point of the low amplitude current waveform S1, using a thyristor, output a predetermined fixed current (6.6 A for example) defined beforehand to be used for lamps or other airport equipment, and supply to the power line.
Therefore, the current immediately after the phase control varies generally in a rapid rise state, presents a high frequency equal or superior to 50 Hz/60 Hz in respect of frequency, transits to a standard waveform (sinusoidal wave) of 50 Hz/60 Hz when in attains the high amplitude current waveform, but happens to be unstable immediately after this transition.
There, conventionally, in the case of transfer of a required signal using a power-line carrier, control, monitoring or other signals are transferred using the power-line carrier, by modulating them with a predetermined frequency from a power line mode which is a part of signal processing system, for the high amplitude waveform S2 at such a timing to avoid the low amplitude current waveform on the power line and rapid rise portions immediately after the phase control, and further, unstable portions during the transition to the high amplitude current waveform, namely noise producing portions.
However, the aforementioned monitoring and control system aims only to transfer the signal at an appropriate timing, noise still generates from the fixed current generator by the phase control, and under the influence of this noise, the reception sensibility of host station and respective terminal deteriorates considerably. In addition, this noise is a spike noise generated like as impulse, and moreover, it is extremely difficult to eliminate, as the noise generation point varies according to the tap position (phase control angle) adjusting the lamp brightness.
Also, in the host station and respective terminal, the control signal and monitoring signal are carried by the power line, using a power line circuit including power line, rubber transformer or the like; however impedance due to LC exists in the power line circuit, and this impedance absorbs signal carried by the power line. This is caused mainly by resonance phenomenon between the rubber transformer reactance L component and the power line and ground capacitance, and there exist abnormal attenuation points of signal carried by the power line. As the result, terminals at the position corresponding to the abnormal attenuation point drop remarkably in their reception sensibility due to the attenuation of carried signal.
Especially, in the case of power-line carrier, abnormal attenuation point is an inevitable problem, because rubber transformers constituting a number of reactance components are installed in the power line circuit. And further, the installation of rubber transformer being dependent on the lamp location in the airport, and can not be decided arbitrarily, the abnormal attenuation amount increases inconveniently according to the installation mode.
It is an object of the present invention to provide a power-line carrier airport facilities monitor system for allowing to transfer stably host station control signal and status signal of lamp, sensor and the like of a number of terminals, and allowing to transfer effectively a quantity of data.
Another object of the present invention is to provide a monitoring control system using the power-line carrier for reducing the effect of noise produced by the fixed current generator, and also to ensure a high quality transfer, without being influenced by the power line circuit construction conditions.
To solve the aforementioned problems, the present invention relates to a power-line carrier airport facilities monitor system, wherein a host station and respective terminals for monitoring and controlling individually the object facilities such as lamp, sensor and the like respectively via a rubber transformer are connected in series to a power line derived from a fixed current generator, the host station transmitting to the respective terminal using power-line carrier based on a control signal from a higher order system, while the respective terminals transmitting the monitoring signal from the object facilities to the host station using power-line carrier, wherein the host station and terminal comprise:
zero cross detection means for detecting the zero cross of power source waveform of the power line, a data processing calculation control section for creating a control command for respective terminal/monitoring signal of the object facilities as text data, and signal insert means for inserting the text data to the power line by FSK modulation based on the zero cross detected by the zero cross detection means.
According to the invention, adopting the aforementioned configuration, it is possible to avoid the prevention magnetic saturation, the text data to be inserted into the power line is transmitted by frequency modification, and as this frequency modulation, it is transmitted by FSK modulation using two frequency modulation, allowing to transmit avoiding stationary noise generated by the fixed current generator (CCR/CCT) creating a fixed current from the commercial power source, and to realize a stable, and, appropriate power-line carrier of the text data without being affected by the noise.
Also, to solve the aforementioned problems, the present invention relates to a monitoring control system using power-line carrier, wherein a host station and respective terminals for monitoring and controlling the facilities to be monitored respectively via a rubber transformer are connected in series to a power line derived from a fixed current generator, the host station transmitting a control signal from a higher order system to the respective terminal by power-line carrier, while the respective terminals monitors the facilities to be monitored upon reception of the control signal and, at the same time, transfers a monitoring signal of this facilities to be monitored by power-line carrier, wherein a bypass filter apparatus comprises a LC resonance circuit resonating with the frequency used for the power-line carrier is provided on the output side power line of the fixed current generator, and noise generated from the fixed current generator and signal of the frequency used for the power-line carrier between the host station and each terminal are respectively separated.
The present invention, adopting the aforementioned configuration, installs a filter apparatus including a LC resonance circuit resonating the frequency used for the power-line carrier and sends noise generated from the fixed current generator to the power source generation side by the filter apparatus, and on the other hand, sends signal transmitted and received between the host station and the terminal to the host station and terminal side by means of the filter apparatus, thus separates noise and signal completely, improving the signal transfer quality.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.